Design: Fixing Wright's Wrongs

A master mason takes the architect to school

by Aaron
Hoover
Few masons would call concrete block walls art, and Ken Uracius
is no exception. But Uracius, who specializes in historic masonry
preservation, feels the word squares up nicely with the main
structural elements of the buildings in his latest project: a
little-known Florida college campus designed by Frank Lloyd
Wright.

"Usually when you get into block work, it's just unitary, nothing
fancy," says Uracius, of Holden, Mass., who travels the nation
restoring old masonry buildings. "This block work is actually
making a statement."

But as sometimes happens with art, Wright's unique system of
grooved block and rebar composing a dozen buildings at Florida
Southern College in Lakeland, Fla., has proved more aesthetic than
practical. A half-century after they were finished, the nation's
largest single collection of Wright-designed buildings is
crumbling.

Lesson for architects: A stellar design, such
as Frank Lloyd Wright's for a series of buildings at Florida
Southern College, must still contend with practical reality. In
this case, the harsh Florida climate has taken a toll out of the
elaborate masonry, requiring the down-to-earth attentions of mason
Ken Uracius.

Building a Legacy

Wright is known for his low-slung Prairie-style homes in the
Midwest. But when then Florida Southern President Ludd Spivey sent
Wright a telegram in 1938 seeking a meeting about "plans for a
great education temple in Florida," Wright didn't hesitate.

"I think he was excited about leaving a legacy for himself in terms
of a fairly large composition of buildings," says Jeff Baker, an
Albany, N.Y.-based architect in charge of the Florida Southern
restoration. "But I think he was also attracted by the opportunity
to leave his mark on future generations."

Spivey's telegram to Wright led to 12 signature structures
completed between 1941 and 1958. Perhaps the most spectacular is
the Water Dome, a circular pool ringed with jets that create a dome
of water. The dome never functioned as Wright intended —
until October, when it became the first major project completed in
the estimated $50 million restoration. The chapel, with its
elaborate iron tower and covered walkways, which Wright called
Esplanades, is among the other items getting attention.

Material Matters

Wright liked to use indigenous materials — a concept that is
making its way back into the industry via the green building
movement — and he tapped coquina from the site in some of the
first buildings, Baker says. But he relied far more on another
Florida resource: sand. Trucked south from St. Augustine, the sand
was the prime ingredient in the three-and-a-half-inch "textile
blocks" used to face all the buildings. Workers built the blocks on
site with a concrete mixture and wooden molds.

The design was unique, and as it turns out, uniquely flawed. Each
block has smooth faces and sides, but is indented with beveled
squares or half-round circles at the edges where a block butts
against its neighbor. Rather than mortar the blocks atop each other
in the long tradition of masonry, Wright stacked them with no
mortar at all, relying instead on a gridwork of horizontal and
vertical grooves to accept rebar, and filling the cavities around
the rebar with grout.

Master mason Ken Uracius grouts blocks on a test wall of a
campus pumphouse, taking care to pack the grout evenly to avoid
pockets where water can collect.

That seemed to work fine, but not for long, Uracius says. The wet
grout typically failed to flow down the grooves between courses or
the narrow cores within the blocks, resulting in pockets where the
rebar remained exposed. As time passed, water found its way in,
sometimes by soaking directly through the porous block. As the
rebar rusted, it expanded. Because the grooves were so narrow, this
was enough to dislodge the grout and crack the block, exploding the
walls from within.

Some fared better than others, but restoring all 12 buildings will
require thousands and thousands of new blocks, Uracius said. After
eight months tinkering with a large experimental wall (the pump
room of the Water Dome, which has served as the mason's de facto
laboratory), Uracius thinks he can stick to Wright's design, partly
by building the blocks with more consistent and better materials.
For the walls, he thinks he can use stainless steel rebar and a
layer of silicon between each block. The seal the silicon creates,
he says, will allow him to fill the grooves with mortar under
pressure.

Water intrusion into the porous block caused the high-iron
steel rebar specced by Wright to corrode, and the expansion of the
iron in the narrow cores blew apart the block over time. In his
day, steel was a new, wondrous material that was supposed to last
forever, but material science had yet to catch up to the
architect's innovations.

Wright's design called for seamless joints between blocks.
Wright referred to the bricks as "textile blocks" both for their
textures and for the method by which they were "woven together"
with steel. Uracius called for stainless steel reinforcing for the
new walls, and given the importance of the rebar in the wall's
design, this is hardly an extravagance.

Uracius said that when he first arrived in Florida, he thought
Wright was insane. "But they sort of grow on you, these buildings,"
he said. "Now I'm kind of interested in seeing what I can do."
Aaron Hoover of Gainesville, Fla., is a
frequent contributor to Coastal Contractor.

The Remaking of Wright's Blocks

In accordance with Wright's belief that each structure should be
composed of inexpensive local materials that grow out of the
ground, the blocks used in the 12 buildings at Florida Southern
College were formed from coquina and sand — both from Florida
— and cement. Their dimensions, 3 feet by 9 inches, were,
like all the measurements in Wright's campus design, divisors of
18, the standard number of feet between orange trees in the groves
surrounding the college at the time. The indents in their surfaces
and the colored glass inserts in some of the buildings blocks call
to mind origami folds and textile patterns, alternating light and
shadow in motifs that carry throughout the collection.

According to master mason Ken Uracius, the blocks failed because
the material science of the day hadn't caught up to Wright's design
criteria. The first flaw was in the recipe itself. Wright used a
sand mix that was evenly graded, allowing for bigger air pockets
and greater vapor permeability. We learned 50 years later the
importance of sand gradation, said Uracius, explaining that when
sand includes more grain sizes, smaller grains fill in the
interstices between larger ones. The new mix includes a wide range
of sizes and a higher percentage of cement.

Using a pneumatic ram, Haley Mills tamps the coquina, sand, and
cement mixture into Wright's original molds. A key to the
performance of the blocks is a graded aggregate — a range of
sand particles that allows for denser packing, ultimately leading
to a more impervious block.

More detrimental was the use of iron rebar. Because the architect
wanted no visual separations between his blocks, he embedded iron
rods in the walls to hold the wall together in lieu of mortar. An
ineffective grouting technique contributed to the problem: where
there was no grout, water collected in the grooves, corroding the
reinforcing. Wright had no way of knowing that iron would rust like
that, said Uracius. It was supposed to last forever.

Uracius said that the biggest challenge was that without mortar
joints, builders lose a key method for keeping walls even:
adjusting the amount of mortar between blocks. It's hard to cover
up errors when you're running block to block, says Uracius. With no
mortar, any variations in block size must be adjusted in the blocks
themselves. Because Wright's design calls for several different
molds for each wall, variations are common and a challenge that
adds days to the job of building a wall. Uracius is still
experimenting to find the best technique for assembling the blocks.
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